分子动力学方法模拟不同温度下铀酰在叶腊石上的吸附和扩散行为

发布时间：2018-06-07 04:27

本文选题：叶腊石 + 铀酰　；参考：《物理化学学报》2017年10期

【摘要】：采用分子动力学方法研究了铀酰在叶腊石表面的吸附和扩散。在碳酸根离子存在的情况下,探究了温度对铀酰吸附和扩散的影响。碳酸根离子与铀酰存在较强的作用力,不同数目的碳酸根离子与铀酰结合会形成多种铀酰种态。在不同温度的模拟中,得到了UO_2~(2+)、UO_2CO_3、UO_2(CO_3)_2~(2-)、UO_2(CO_3)_3~(4-)四种铀酰种态和铀酰聚合物。通过原子密度图,观察了粒子在溶液中的分布情况。发现UO_2~(2+)+和UO_2CO_3容易吸附在叶腊石上,而UO_2(CO_3)_2~(2-)和UO_2(CO_3)_3~(4-)主要存在于扩散层中。随着时间的推移,越来越多的碳酸根离子与铀酰配位,使得铀酰在叶腊石上的吸附逐渐减少。本文计算了不同温度下,各铀酰种态的扩散系数。在扩散层中,各种态的扩散系数随温度的变化较为一致,而在吸附层中,UO_2~(2+)和UO_2CO_3的扩散速率随温度的变化较UO_2(CO_3)_2~(2-)和UO_2(CO_3)_3~(4-)慢。但是在同一温度下,同一个吸附层或扩散层中,铀酰种态的扩散系数大小顺序始终保持不变:UO_2~(2+)UO_2CO_3UO_2(CO_3)_2~(2-)UO_2(CO_3)_3~(4-)。说明在碳酸根存在的情况下,UO_2~(2+)可能是主要的扩散形式。
[Abstract]:The adsorption and diffusion of uranyl on the surface of pyrophyllite were studied by molecular dynamics. The effect of temperature on the adsorption and diffusion of uranyl was investigated in the presence of carbonate ions. There is a strong interaction force between carbonate ion and uranyl, and different numbers of carbonate ions combine with uranyl to form a variety of uranyl species. In the simulations at different temperatures, we have obtained four types of uranyl species and uranyl polymers in UO_2~(2 / UO _ 2C _ _ _ The distribution of particles in solution was observed by atomic density diagram. It is found that UO_2~(2) and UO_2CO_3 are easily adsorbed on pyrophyllite, while UO _ s _ 2CO _ 3 / T _ 2) and UO _ s _ 2C _ 3 / C _ 3) are mainly found in the diffusion layer. With the passage of time, more and more carbonate ions coordinate with uranyl, which makes the adsorption of uranyl on pyrophyllite decrease. The diffusion coefficients of each uranyl state at different temperatures have been calculated. In the diffusion layer, the diffusivity of various states is more consistent with the temperature, but the diffusion rate of UO _ 2S _ 2 and UO_2CO_3 in the adsorption layer is slower than that of UO _ 2C _ 2C _ 3C _ 2T _ 2 and UO _ 2C _ 3s _ T _ 3s _ 2) and UO _ 2C _ 3s _ T _ 3s _ T _ 4) in the adsorption layer. However, at the same temperature, the order of diffusion coefficients of uranyl species in the same adsorption or diffusion layer remains unchanged. It is suggested that UO _ 2C _ 2) may be the main diffusion form in the presence of carbonate.
【作者单位】：北京分子科学国家实验室放射化学与辐射化学重点学科实验室北京大学化学与分子工程学院;中国工程物理研究院核物理与化学研究所;
【基金】：高放废物地质处置专项资金(2007-840,2012-851) 国家自然科学基金(U1530112,11475008,11075006,91026010)资助项目~~
【分类号】：O647.3

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